I had a central air ac unit lose all coolant over the weekend. The guy i had look at it said that it probably is a major leak that to replace would cost $1200 on a low end (contractor build) unit that is already 6 yrs old. He suggested buying a new unit with install for $3500. I have Sears coming today to give a quote on a new unit as well. Any suggestions? Seems like 6yrs old is young. I probably ran the unit for 24 hours without coolant. Guy said that damaged compressor as well. help. -SA